Fluid system and valve assembly therefor



Jan. 24, 1967 H. J. ST CEY 3,2

FLUID SYSTEM AND VALVE ASSEMBLY THEREFOR Filed March 26, 1964 25 -28-4,741 "w J 6 L INVENTOR HUM! of 57:4,;

United States Patent 3,299,903 FLUID SYSTEM AND VALVE ASSEMBLY THEREFORHugh J. Stacey, Chesterland, Ohio, assignor to Parker- I-IannifinCorporation, Cleveland, Ohio, a corporation of Ghio Filed Mar. 26, 1964,Ser. No. 355,010

4 Claims. (Cl. 137118) The present invention relates generally asindicated to a fluid system and valve assembly therefor and moreparticularly to a system having a valve therein which eliminates pumpcavitation as would otherwise be caused, for example, by a fluid motorbeing fluid-pressure actuated in the same direction as the applied loadon the motor.

It is a principal object of this invention to provide a fluid systemwhich comprises a pump, a reservoir, one or more fluid motors, and adirectional control valve assembly having therein one or more valvespools to control the flow of fluid to and from the respective motors,said assembly incorporating therein a novel flow control valve whichprevents pump cavitation as aforesaid.

It is another object of this invention to provide a simple and compactdirectional control valve assembly for one or more fluid motors whichhas incorporated in the housing thereof a novel flow control arrangementwhich maintains a positive pressure in the inlet despite tendency of amotor piston to move under heavy applied load at a rate exceeding thepump capacity.

Yet another object is to provide a fluid system in which all of thereturn fluid from the motors is transferred to the inlet when the inletpressure drops below a predetermined value, thereby supplementing theamount of fluid supplied to the inlet by the pump.

Still another object is to supply such return fluid to the inlet fromthe motors at high pressure for rapid flow.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds.

valve assembly in association with-a pump, a reservoir,

and a pair of fluid motors, such section of the control valve assemblyhaving been taken substantially along the line 1-1, FIG. 2; and

FIG. 2 is a cross-section view the line 22, FIG. 1.

As shown in FIG. lot the drawing, herein shown comprises a pump 1, afluid reservoir 2, a pair of fluid motors 3, 4, and a directionalcontrol taken substantially along the fluid system valve. assembly 5.Said assembly 5 comprises a housing 6 having an inlet port 7 connectedtothe pump delivery conduit 8, a return port 9 connected by conduit 10 tothe I reservoir 2, a pair of service ports 11, 11 connected by conduits12, 12 with the ends of the fluid motor 3, and

15 wit-h the ends of the fluid motor 4.

The housing 6 is formed with bores 16, 17 in which the respective valvespools 18, 19 are reciprocable to control the respective fluid motors 3,4. When both a pair of service ports 14, 14 connected by conduits -15,-

spools 18 and 19 are in neutralpositiorl as shown, both motor pistons 20and 21 are locked against movement in either direction and the fluiddischarged by the pump 1 is bypassed to the reservoir 2 via the bypasspassage 23 which intersects the respective bores 16 and 17.

Straddling the bypass branches 24, 24 and 25, 25 which intersect therespective bores '16 and 17 are pressure feed passages 26, 26 and 27, 27which communicate with the inlet chamber 28 through check valves 29which, as well-known in the art, are so-called load check valves toprevent reverse flow of fluid from one motor circuit to another whenboth are operated simultaneously, as in the case where one motor isoperating under greater load than the other motor. Straddling therespective pressure feed passages 26, 26 and 27, 27 are the aforesaidservice ports 11, 11 and 12, 12, and straddling the respective serviceports 11, 11 and 12, 12 and intersecting both bores 16 and '17 arereturn passages, 30, 30 which, in a con ventional form of control valveassembly, would communicate directly with the return chamber 31.

However, in the present case said return passages 30, 30 communicatewith the return chamber 31 through return passage 32 and the openings 34in the spring-biased flow control valve 35 as shown in FIG. 2. Thereturn passages 39 also communicate with the inlet chamber 28 throughthe check valve 36 so that fluid may flow from the return passages 30into the inlet chamber 28 whenever the pressure in the return passages30 exceeds the pressure in the inlet chamber 28.

The return passage 32 also leads to the chamber 37 which is communicatedwith the inlet chamber 28 through a relief valve 38, whereby wheneverthe fluid pressure in the inlet chamber 28 builds up to a desiredmaximum as determined by the setting of the relief valve 38, the excessfluid will be returned to the reservoir 2 via the chamber 37 for returnpassage 32 and return chamber 31 thus to prevent build up of pressureabove said predetermined maximum.

Referring in detail to the flow control valve 35, it comprises a tubularvalve member which is biased by the spring 39 to the position shown inFIG. 2, in which communication is blocked thereby between the returnpassages 30 and the return chamber passage 32 because the openings 34through the valve member 35 are blocked by the land 40 between saidpassages.

The valve spool 18 is of conventional four-way open center type and whenit is moved downwardly from the position shown in FIG. 1, the upper feedpassage 26 is communicated with the upper service port 11, whereby fluidunder pressure in the inlet chamber 28 will flow into the rod end of themotor 3. In this position of the spool 18, the lower service port 11 iscommunicated with the lower return passage 30, whereby fluid displacedfrom the head end of the motor 3 will flow into said lower returnpassage 30. Since normally there is suflicient fluid pressure in theinlet chamber 28 to actuate the motor 3 as aforesaid, such fluidpressure through the passage 41 will act on the annular area of the flowcontrol valve member 35 to urge it toward the left to bring the openings34 therethrough in register with the return passage 30, and thus thedisplaced fluid will flow the return passage 30 through the openings 34and into the return passage 32 and chamber 31 to the reservoir 2.

Now, in the event of a heavy load acting on the piston 20 tending tomove it rapidly toward the left to require more fluid than is availablefrom the pump '1, there will be a drop in pressure in the inlet 7 to thepoint where the pressure acting on the valve member 35 is ins-ufficientto maintain the valve member in its aforesaid left open position. Inthat case the spring 39 biases the valve member 35 to the position shownin FIG. 2 to cause a build up in pressure in the return passage 30 whichthen will open the check valve 36 to assist in maintaining pressure andsupplying additional fluid into the inlet chamber 28. As is readilyapparent, so long as the valve member 35 remains in the closed position,all of the return fluid from the fluid motor 3 will be directed to theinlet chamber '28 via the check valve 36 for recirculation through thedirectional control valve 5-. Moreover, since the pressure of the returnfluid in the return passages 30 does not act on the valve member 35tending to move the same to the open position, the pressure at which thereturn fluid is transferred from the return passages 30 to the inletchamber 28 can be quite high for rapid flow, the amount of pressuredepending, among other things, upon the weight of the load tending tomove the piston 20 in the same direction in which it is being fluidacuated. Only when the inlet pressure again reaches a value sufficientto cause actuation of the valve member 35 to the open position, will thepressure in the return passages30 be relieved through the return chamber31.

When the pressure in the inlet chamber 28 again builds up to the pointwhere the valve member 35 is shifted to.

the left, the piston 20 will be acuated by fluid pressure to the leftwithout causing pump cavitation.

The flow control valve 35 operates in the same manner as above-describedwhen the spool 18 is shifted upwardly from its neutral position to causeactuation of the fluid motor 3 in the opposite direction, and if theload on the piston 20 acts to tend to move it rapidly toward the right,the flow control valve 35 will prevent cavitation in the pressurecircuit leading to the head end of the fluid motor 3.

The other valve spool 19 is also of the four-way open center type buthas an additional operating position, namely, a float position, in whichthe service ports 27, 27 are communicated with each other through thebore 42 and slots 43 of the spool 19 and with the bypass 23 a throughthe orifice 45 which extends radially into bore 42. Thus, in the floatposition when a load is acting to move the piston 21 toward the leftsuch movement is permitted at a controlled rate of speed with the excessfluid from the head end being conducted to the reservoir= 2 via theorifice 45. When piston 21 floats toward the right, fluid flows into thehead end of motor 4 through orifice 45.

Within the cap assemblies 46 and 47 secured to the valve housing 6 arethe usual forms of spool centering spring mechanisms, and suitabledetent mechanisms for yielda-bly retaining said spools 18 and 19 in oneor mor operating positions.

When the spool 19 is actuated to its operating positions to move thepiston 21 in opposite directions, the flow control valve 35 will operatein the manner already described to prevent cavitation of the pressurecircuit, and return fluid from the motor 4- will be conducted via thecheck valve 36 into the inlet chamber 28 to help maintain higherpressure therein should the rate of movement of piston 21 tend to exceedthe pump capacity.

By way of example, the directional control valve assembly 1 is of themultiple spool type arranged so that either or both spools may beoperated independently or simultaneously. However, it is to beunderstood that the check valves 29 for the downstream spool 19 may havetheir inlets in the bypass portions 25 between the spools 18 and 19,substantially as shown in the patent to Herbert H. Schmiel, US. PatentNo. 3,000,397, granted Septemv It is to be noted that if the pressure ininlet port 7 decreases gradually, the return flow through openings 34will likewise gradually decrease to effect a gradual build up ofpressure in the return passages 30. Such build up of pressure in thereturn passages 30 opposes movement of the piston 20 and 21 under loadand when the pressure in return passages 30 exceeds that in the inletchamber 28, the check valve 36 will be opened to supplement the fluidsupplied by pump 1.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims, or the equivalent ofsuch, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In combination, a directional control valve and a flow control valve,said directional control valve comprising a housing having an inlet portfor communication with a fluid pressure source, a return port, a pair ofbores, and a pair of motor ports associated with each bore, said boresbeing intersected axially therealong by passages communicating with saidinlet, return, and motor ports, a valve spool in each bore movable tooperating positions whereat communication is established selectivelybetween said inlet passage and one of its associated motor ports whilethe other associated motor port is communicated with said returnpassage, and mean including a check valve operative to permit flow offluid from said return passage to said inlet port when the pressure insaid inlet port is lower than the pressure in said return passage tosupplement the fluid in said inlet port which is already being suppliedby said fluid pressure source; said flow control valve comprising avalve means located in said return passage downstream of both of saidvalve spools operative to block return flow from said motor portsthrough said return passage to said return port when the pressure insaid inlet port drops below a predetermined value to cause a buildup ofthe pressure in said return passage, whereby the discharge from all ofsaid motor ports will be directed to said inlet port to provide makeupflow for said .directional control valve when the pressure in said inletpassage drops below such predetermined value.

2. The directional control valve of claim 1 wherein said housing has abypass passage communicating said inlet port with said return port whensaid valve spools are in a neutral position, and the inlet passages forthe downstream valve spool communicate with said bypass passage betweensaid valve spools, whereby only one valve spool at a time may be movedto an operating position as aforesaid.

3. The combination of claim 1 wherein the inlet passages for thedownstream valve spool communicate with said inlet port upstream of theother valve spool, whereby either or both valve spools may be operatedindependently or simultaneously.

4. In combination, a directional control valve and a flow control valve,said directional control valve comprising a housing having an inlet portfor communication with a fluid pressure source, a return port, and apair of motor ports, said housing having a bore intersected axiallytherealong by passages communicating with said inlet, return, and motorports, a valve spool movable insaid bore to operating positions whereatcommunication is established selectively between said inlet passage andone motor port while the other motor port is communicated with saidreturn passage, and means including a check valve operative to permitflow of fluid from said return passage to said inlet port when thepressure in said inlet port is lower than the pressure in said returnpassage to supplement the fluid in said inlet port which is alreadybeing supplied by said fluid pressure source; said flow control valvecomprising a valve means operative to block return flow from said motorports through said return passage to said return port when the pressurein said inlet port drops below a predetermined value to cause a buildupof the pressure in said return passage, said valve means being disposedin said return passage and defining with the housing of said directionalcontrol valve a fluid chamber, a passage leading from said inlet port tosaid fluid chamber, said valve means having a plurality of openingsthrough one end and an annular shoulder adjacent the other end exposedto fluid pressure in said chamber tending to move said valve means to aposition whereat return fluid is permitted to flow through said returnpassage via said openings in said valve means to said return port, andspring means in said 10 housing biasing said valve means to a positionWhereat said openings in said valve means are blocked by a land in saidreturn passage when the pressure in said inlet port and thus in saidchamber is below such predetermined value.

References Cited by the Examiner UNITED STATES PATENTS Deardorfi et a1.91420 Tennis 91-436 X Schmiel 137596.13

Tilney 91-420 Gondek 91420 Westveer 91420 Tennis 137596.2 X

5 P. E. MALOUSKY, H. KLINKSIEK,

Assistant Examiners.

1. IN COMBINATION, A DIRECTIONAL CONTROL VALVE AND A FLOW CONTROL VALVE,SAID DIRECTIONAL CONTROL VALVE COMPRISING A HOUSING HAVING AN INLET PORTFOR COMMUNICATION WITH A FLUID PRESSURE SOURCE, A RETURN PORT, A PAIR OFBORES, AND A PAIR OF MOTOR PORTS ASSOCIATED WITH EACH BORE, SAID BORESBEING INTERSECTED AXIALLY THEREALONG BY PASSAGES COMMUNICATING WITHSRAID INLET, RETURN, AND MOTOR PORTS, A VALVE SPOOL IN EACH BORE MOVABLETO OPERATING POSITIONS WHEREAT COMMUNICATION IS ESTABLISHED SELECTIVELYBETWEEN SAID INLET PASSAGE AND ONE OF ITS ASSOCIATED MOTOR PORTS WHILETHE OTHER ASSOCIATED MOTOR PORT IS COMMUNICATED WITH SAID RETURNPASSAGE, AND MEAN INCLUDING A CHECK VALVE OPERATIVE TO PERMIT FLOW OFFLUID FROM SAID RETURN PASSAGE TO SAID INLET PORT WHEN THE PRESSURE INSAID INLET PORT IS LOWER THAN THE PRESSURE IN SAID RETURN PASSAGE TOSUPPLEMENT THE FLUID IN SAID INLET PORT WHICH IS ALREADY BEING SUPPLIEDBY SAID FLUID PRESSURE SOURCE; SAID FLOW CONTROL VALVE COMPRISING AVALVE MEANS LOCATED IN SAID RETURN PASSAGE DOWNSTREAM OF BOTH OF SAIDVALVE SPOOLS OPERATIVE TO BLOCK RETURN FLOW FROM SAID MOTOR PORTSTHROUGH SAID RETURN PASSAGE TO SAID RETURN PORT WHEN THE PRESSURE INSAID INLET PORT DROPS BELOW A PREDETERMINED VALE TO CAUSE A BUILDUP OFTHE PRESSURE IN SAID RETURN PASSAGE, WHEREBY THE DISCHARGE FROM ALL OFSAID MOTOR PORTS WILL BE DIRECTED TO SAID INLET PORT TO PROVIDE MAKEPFLOW FROM SAID DIRECTIONAL CONTROL VALVE WHEN THE PRESSURE IN SAID INLETPASSAGE DROPS BELOW SUCH PREDETERMINED VALUE.